John S. Jacob, Kirana Pandian, Ricardo Lopez, and Heather Biggs
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ERPT-002 TAMU-SG-14-303 5/14 John S. Jacob, Kirana Pandian, Ricardo Lopez, and Heather Biggs Houston-Area Freshwater Wetland Loss, 1992–2010 John S. Jacob Director Texas Coastal Watershed Program Kirana Pandian Ricardo Lopez Heather Biggs Former Extension Associates Texas Coastal Watershed Program The Texas A&M University System Acknowledgments This publication is supported in part by an institutional grant to the Texas Sea Grant College Program (NA10OAR4170099) from the National Sea Grant Office of the National Oceanic and Atmospheric Administration, U.S. Department of Com- merce. The Galveston Bay Estuary Program funded phase one of this work. The SSPEED Center at Rice University funded a portion of the current project. Steven Pennings, Anna Armitage, and Andrew Sipocz provided very helpful reviews. Rebecca Davanon provide cartographic assistance for the final publication. Unless otherwise noted, all photographs were taken by John S. Jacob. Summary Since 1992, the Greater Houston Metropolitan Area has lost at least 5.5 percent of its natural freshwater wetlands. Although a 5 percent loss in 20 years is unsustainable by any accounting, some areas experienced loss at rates that are catastrophic. For example, Harris County lost almost 30 percent of its freshwater wetlands, including most prominently the iconic prairie pothole-pimple mound complexes. The eight-county Houston area is one of the fastest growing in the country. Metropolitan growth means development, which means the loss of wetlands. When wetlands are lost, with them go important ecological services for both nature and people. Until now we have not had a clear picture of just how many acres of wetlands we might be losing. We report here our attempt to quantify freshwater, non-tidal wetland loss from 1992 to 2010 in the greater Hous- ton region. We developed a simple method for quickly estimating natural fresh- water wetland loss. The method, a conservative approach that provides a minimal loss estimate that policy makers can rely on, compares National Wetland Inventory (NWI) maps developed in 1992–93 to more recent digital aerial photography. The study found that most of the losses occurred in rapidly growing Harris, Montgomery, Brazoria, and Fort Bend Counties. The greatest loss occurred in Harris County: 15,855 acres (29 percent) from 1992 to 2010. This acreage loss is more than double that of the other seven counties combined. Losses in other rapidly growing counties, however, are on a track to equal that of Harris County. Overall, the study reveals that development is seriously affecting the freshwater wetland resources in the Greater Houston Metro Area. These freshwater wetlands are the headwaters for virtually all of the water bod- ies feeding into Galveston Bay. Continued loss at the rates documented here will very likely have grave implications for the long-term health of the Galveston Bay System because it is losing the principal means of cleaning the polluted runoff that enters the bay. A three-page synopsis on this study, More Flooding, Fewer Fish: Freshwater Wetland Loss in the Houston Area, 1992–2010, is available from the Texas A&M AgriLife Service Bookstore at https://www.agrilifebookstore.org/. Contents Introduction .............................................................................................................................1 Study area ...........................................................................................................................1 Types of freshwater wetlands in the study area ..............................................................2 Methodology .............................................................................................................................3 The tradeoff: sampling versus complete inventory ........................................................3 Cowardin classification..................................................................................................... 6 Artificial and farmed wetlands .........................................................................................7 Logging ................................................................................................................................8 Results .......................................................................................................................................8 Wetland loss in the context of recent Supreme Court rulings on wetlands ...................11 SWANCC ..........................................................................................................................11 Rapanos .............................................................................................................................11 Implications ............................................................................................................................12 Loss of services .................................................................................................................12 What can be done? ...........................................................................................................13 References ................................................................................................................................14 Appendix A: Wetland loss by county ..................................................................................15 Appendix B: Graphs ..............................................................................................................17 Appendix C: Atlas of wetland loss .......................................................................................21 Appendix D: Cowardin Classification ................................................................................34 Appendix E: Freshwater wetland loss geo-spatial data processing .................................41 Figures Figure 1: A coastal prairie pothole wetland in southeast Harris County .........................1 Figure 2: Project study area: the Greater Houston Metropolitan Area .............................1 Figure 3: Barrier island interior wetlands .............................................................................2 Figure 4: Coastal flatwoods wetlands ...................................................................................2 Figure 5: Prairie pothole with encroaching development ..................................................3 Figure 6: Riverine forested wetlands, Houston ....................................................................3 Figure 7: NWI wetland polygon converted into Residential classification ......................4 Figure 8: NWI wetland polygons converted into C/I category ..........................................5 Figure 9: NWI wetland polygon converted into Fill classification ....................................5 Figure 10: NWI wetland polygon converted into Water features ......................................5 Figure 11: NWI wetland polygons converted into Mining category .................................6 Figure 12: Farmed wetlands indicated in northwest Harris County ................................7 Figure 13: Farmed wetland delineation Chambers and Liberty Counties........................7 Figure 14: Farmed wetlands with potholes ...........................................................................7 Figure 15: (a) Forested wetland in a deforested state, and (b) forested wetland after 6 years in a regrown state .......................................................................................8 Figure 16: Graph of wetland loss by county ..........................................................................9 Figure 17: Total natural freshwater wetland loss in Greater Houston Metro Area ..............9 Figure 18: Harris County wetland loss in acreage and percentage by each period ........9 Figure 19: The White Oak Bayou watershed lost 71 percent of its wetlands (shown in red) from 1992 to 2010 ....................................................................................9 Figure 20: The Cypress Creek area lost 29 percent of its wetlands (shown in red) from 1992 to 2010 .............................................................................................................9 Figure 21: The Spring Creek area lost 11 percent of its wetlands (shown in red) from 1992 to 2010 ...........................................................................................................10 Figure 22: Harris County wetland loss under FEMA 100-year floodplain ...................11 Figure 23: A prairie pothole marsh in Harris County .....................................................13 Figure 24: A freshwater marsh .............................................................................................14 Tables Table 1: Palustrine wetlands classes ......................................................................................6 Table 2: Wetland loss by county .............................................................................................8 Table 3: Wetland loss by type of destruction ......................................................................10 Table 4: Total wetland loss by wetland type, Greater Houston Metro Area ..................10 Table 5: Wetland loss with respect to the FEMA 100-year floodplain ............................12 Introduction The population of the Greater Houston Metro- While somewhat imprecise because of the limita- politan Area is skyrocketing, particularly in Hous- tions of the source data, this method is more than